tl;dr Are these adapters just bad, or am I missing how to make them fit?

So I decided to upgrade my dust collection this season and finally add some PVC ducting instead of just moving the hose from tool to tool, as well as build a cyclone. I got Powertek’s 4” PVC to hose adapters, as well as their cyclone kit. Put all my PVC in how I wanted it, stuck the adapters in the fittings, and I cannot get my flex hose to fit over them. I was able, with the help of another person, to wrestle a hose onto one of the cyclone fittings, and expect to be able to do the same for the other, but the adapters are just the wrong diameter. Even after sanding close to 1/8” from all sides of one, the hose is still not going on.

I have 2 different brands of flex hose, and they both fit fine over my dust collector port, my blast gates, and the ports on my tools, so I’m pretty sure it’s not a hose issue. Did I just get a bad batch of Powertec adapters? Is there a trick I’m missing to attaching them? Or should I just abandon them and order Rockler instead?